In a data communication system equipped to a vehicle, a duplex data communication is required to be performed using single wire harness or two paired wire harnesses for differential signaling so that total weight of the wire harnesses is reduced. When the data communication is performed between an electronic control unit (ECU) and a sensor (or an actuator), an increase in cost is required to be restricted in the sensor or the actuator. In an application that does not require a high-speed data communication rate, a wire harness may be used as a transmission line that performs duplex data communication. Herein, the transmission line may perform the duplex data communication based on a time division multiplexing that is used in distributed system interface 3 (DSI3) or in peripheral sensor interface 5 (PSI5). However, in an application that requires a high-speed data communication rate, the time division multiplexing may cause a deterioration in transmission efficiency.
On the other hand, when the data communication is performed simultaneously in bidirectional without performing the time division multiplexing, signal interference occurs and received data cannot be reproduced from the received signal waveforms. Usually, a clock data recovery (CDR) process that extracts a clock signal from a received signal is used to synchronize a communication rate. However, a transmission signal affects a signal waveform of itself, and the clock signal extracted by the clock data recovery has a relatively large amount of error. Regarding above-described difficulties, duplex data communication using single wire harness without performing time division multiplexing may be performed in the following two methods.
The first method is dividing a communication signal frequency. As shown in Fig. 5 of “IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 47, NO. 8, AUGUST 1999 Zipper: A Duplex Method for VDSL Based on DMT”, a bandwidth of a digital subscriber line (DSL) may be divided in order to perform the duplex data communication using single wire harness. The second method is subtracting the transmission signal of own device from the received signal that is transmitted from a different device. As shown in Fig. 3 of “IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 36, NO. 3, MARCH 2001 A 125-MHz Mixed-Signal Echo Canceller for Gigabit Ethernet (registered trademark) on Copper Wire”, a digital processor cancels a transmission data and an echo component of the transmission data from a received data by performing a signal processing in order to perform the duplex data communication using single wire harness.
However, in the first method, a modulation and demodulation circuit for frequency conversion is additionally required, and accordingly, a circuit structure becomes complicated compared with a normal case in which the modulation and demodulation of the frequency is not required. In addition, the complicated circuit structure causes increase in cost. In the second method, an analog-digital converting circuit, a digital-analog converting circuit, and a digital signal processing circuit are additionally required, and accordingly, a circuit structure becomes complicated compared with a normal case in which above-described circuits are not required. In addition, the complicated circuit structure causes increase in cost. As described above, the duplex data communication can be performed using single wire harness with either one of the above-described two methods. However, additional circuits are required in each of the two methods, and the additional circuits required to be added cause increase in cost.